Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
HDFGroup hdf5 — Array full size, element count, and element size are not checked to make sure they match in H5Odtype.c
AV AC AT PR UI VC VI VA CVSS EPSS %ile KEV
N H P N A N N H 5.9 .0027 18.9 —
AFFECTED
Product Versions Fixed
hdf5 < 2.0.0 – —
TIMELINE
Feb 11 Reserved by GitHub_M
Jul 20 EXPLOIT PUBLISHED — CVE-2026-26197 (HDFGroup hdf5). Public exploit reference added.
Jul 20 Published (CNA: GitHub_M)
Description
HDF5 is a high-performance library and a file format specification that implements the HDF5 data model. If a file is corrupted such that an array datatype's size, the number of elements, and the element size are not in agreement it can trigger an out of bounds read. The array datatype stores the full size of the datatype (`dt->shared->size`) separately from the number of elements (`dt->shared->u.array.nelem`) and the element size (`dt->shared->parent->shared->size`). If any one of these are corrupted so that they don't align with the others (element size * nelem = full size), it can lead to an out of bounds read. Depending on what is corrupted, it can alter the type of out of bounds read triggered. The vulnerability is present only in files that have been maliciously altered, as its generally not possible to independently alter the full size of the datatype, the element count and the element size. As such, this is only present if a malicious actor is altering files, and won't appear in regular usage.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| February 11, 2026 | Reserved | Reserved by GitHub_M |
| July 20, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-26197 (HDFGroup hdf5). Public exploit reference added. |
| July 20, 2026 | Published | Published (CNA: GitHub_M) |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| HDFGroup | hdf5 | — | < 2.0.0 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-26197 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.